GC: Fourier Transform Infrared Spectroscopy

The combination of gas chromatography (GC) with Fourier transform infrared spectroscopy (FTIR) has gradually become the important analytical tool for qualitative and quantitative analysis of complex mixtures. Numerous applications have been reported in previous reviews. Separation and identification of components in complex mixtures can be a daunting task. GC is the most common technique for separation of volatile and semivolatile mixtures. It is well accepted that when GC is coupled with spectral detection methods, such as MS, NMR, or FTIR spectrometry, the resulting combination is a powerful tool for the analysis of complex mixtures. FTIR spectroscopy, used as a detector in GC, has many advantages. First, FTIR is the most universal of all detectors currently used in GC, because all organic compounds exhibit IR-active vibrations and, thus, absorb IR radiation. Moreover, these absorptions obey Beer’s law so that the data can be used directly for quantification. Furthermore, FTIR can be used both as a selective and as a specific detector. Finally, the non-destructive character of GC/ FTIR is an important advantage when compared with other detectors; it offers the opportunity to investigate GC eluates after FTIR analysis. However, despite these advantages, FTIR detection is not widely applied in GC analysis at present. This is, particularly, due to its lack of sensitivity; a second reason is the complexity of IR spectra. Yet, the power of GC/FTIR is the unique structural information that can be extracted from the spectral data and that cannot be obtained from any other method. It is, therefore, very likely that, in the next few years, this technique will attract much closer attention from analytical chemists. Although GC/IR was first introduced in the 1960s, its use did not become widespread until the 1980s. Several factors were responsible for its application in GC analysis. That is, particularly, due to its lack of sensitivity and the interfaces.